Catalytic Activity of Expanded Interface between Gold Nanoparticle and Titania Substrate

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We have studied catalysis of gold nanoparticles on TiO2 (Au/TiO2). We directly observed interstitial Ti ion, which has been proposed as a source of an excess electron for O2 activation. Interstitials exists at an interface and/or perimeter of Au/TiO2, whereas they are deficient in a peripheral region of the gold nanoparticles. The interstitials concentrated into the Au/TiO2 interface are consistent with the previous report of the growth of Au/TiO2 interface in O2 exposure, because interstitials react adsorbed O2 to form Ti(1-x)O2 structure, x>0. The interstitial ions at the perimeter/interface of Au/TiO2 are a promising candidate of a source of an excess electron for O2 activation in CO oxidation catalysis. Based on cathode luminescence spectra of Au/TiO2 taken in CO, O2 and CO+O2, we proposed a model that superoxide of Ti(1-x)O2 promotes CO oxidation catalysis.